Maintaining cardiovascular fitness on as little cardio as possible

Just come off a 6 month phase working up my running/cardio ability for a work based role. Little to say it didn't work out.

Currently have a 9:30min 2.4k and are looking to hold onto it with as little running as possible. Trying to drop the running and throw in a lot more sprints/heavy lifting and go back to my shape/size I was while crossfitting and pre endurance training.

Something as simple as 3 x 1km repeats with a sprint session (400,200,100's) be enough to hang onto it?

Would love to hear from anyone with any experience in terms of minimal training for endurance.

Sorry I'm late getting back to you. I do them 3 days/week, & do them full tilt. 2 days would be good, but I like the 3x/week routine. I would probably do longer than 120 yds, but the park where I run has limited space. However, the uphill angle is perfect (a gentle slope). This makes it much easier on the joints. Supposedly there is a study which claims that uphill slopes reduce injuries by up to 30%. I've been doing them for 2 years (barefoot) & my knees have never been stronger (age 53). No warm-up for me... just get out & do it. Run 120 yds/walk 120 yds.

Sorry I'm late getting back to you. I do them 3 days/week, & do them full tilt. 2 days would be good, but I like the 3x/week routine. I would probably do longer than 120 yds, but the park where I run has limited space. However, the uphill angle is perfect (a gentle slope). This makes it much easier on the joints. Supposedly there is a study which claims that uphill slopes reduce injuries by up to 30%. I've been doing them for 2 years (barefoot) & my knees have never been stronger (age 53). No warm-up for me... just get out & do it. Run 120 yds/walk 120 yds.

I doubt you even need the 3 x 1m sessions. One sprint session a week plus some general crossfitesque metcons and some heavy lifting should be fine. By sprint session, I mean short and fast and hard. Something like 10x40m with a minute or so rest in between. Each sprint should be 100% effort, that means the first one will be a lot faster than the last one.